A car bomb in Homs in central Syria Thursday killed six people in an Alawite-majority neighbourhood of the city, a monitoring group said as state media gave a lower toll.
The attack is the second of its kind in a week, and comes just over a month after rebels lost their bastion in the heart of Homs city to regime control.
The Syrian Observatory for Human Rights said at least six people were killed in the attack and nine seriously wounded, adding that it expected the death toll to rise.
State television put the death toll at three, and said women and children were among the nine wounded in what it called a "terrorist car bomb attack in the Akrameh district.
The Britain-based Observatory, which relies on activists and medics on the ground for its reports, was not able to say who was behind the blast.
Homs was once dubbed "the capital of the revolution" against President Bashar al-Assad. Most of the city, except the battered district of Waar, has returned to regime control after two years of bombardment and siege.
Elsewhere, warplanes launched 25 air strikes on Mleiha southeast of Damascus, a key rebel bastion that the regime has struggled for weeks to recapture, the Observatory said.
Regime ground forces also fired surface-to-surface missiles at the Mleiha as troops backed by Lebanon's Shiite Hezbollah battled rebels and their jihadist Al-Nusra Front allies, said the monitor.
The Assad regime in late spring began a bid to retake Mleiha, which is strategically located near the airport road and in the besieged rebel region of Eastern Ghouta.
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Meanwhile, activists in the rebel-held Al-Hajar al-Aswad neighbourhood in southern Damascus accused the regime of cutting off water supplies for more than two weeks.
"Some 20,000 people live here, mostly women and children. The regime wants to pressure civilians into forcing rebels to sign a truce with the army," activist Rami al-Sayed told AFP.
"People are suffering from inflammations and digestive system diseases because they are drinking dirty water from wells," he added.
Rights groups have frequently accused both sides in Syria's conflict, especially the regime, of using illegal siege tactics as a weapon of war.
On another front, an armed group allied to the jihadist Islamic State of Iraq and the Levant (ISIL) on Wednesday kidnapped two Syrian rebel commanders in Deir Ezzor province.
While rebels seeking Assad's ouster initially welcomed ISIL among their ranks, the jihadists' systematic abuses turned the opposition against them.
Rebels and Islamists have fought ISIL since January, pushing them out of large swathes of the north.
ISIL remains squarely in control of Raqa, and is seeking to expand its influence in oil-rich Deir Ezzor province bordering Iraq.
The group already controls many of the Syrian province's energy fields.
It is also leading a militant offensive in Iraq where hundreds of thousands of Iraqis have been displaced in nine days of fighting and an unknown number killed.